Sensitivity and Resistance to Growth Promoting Agents in Animal Lactobacilli

The minimal inhibitory concentrations of 11 growth promoting agents were determined by agar-dilution method against 113 strains of lactobacilli isolated from caeca of pigs, cattle and poultry. Only Lactobacillus acidophilus strains were susceptible to avoparcin and all strains were resistant to copper sulphate. Resistance was noted in cattle and poultry strains against bacitracin, in pig strains against virginiamycin, and in pig and poultry strains against nitrovin. Resistance against carbadox, flavomycin, lincomycin, oleandomycin, spiramycin and tylosin was noted in strains from all three host species.